Several publications show cellular shades, wherein a fabric material is formed to define parallel tubular cells extending horizontally across the width of the shade. Air within each of the cells only circulates minimally, such that when expanded the shades provide good thermal insulation.
It is, of course, desirable to make the physical appearance of the shade as attractive as possible. Similarly, it is desirable to make such shades as economically as possible, which requires both that a minimal amount of material be used to form each cell and that the manufacturing process be as expeditious as possible.
Various exemplary prior art disclosures include the following:
U.S. Pat. No. 2,201,356 to Terrel discloses a window shade made by joining two folded sheets having interior and exterior folds. FIGS. 4 and 5 show an asymmetrical embodiment where the interior folds of one sheet are joined to the exterior folds of the other sheet.
U.S. Pat. No. 3,892,898 to Yasui relates to a honeycomb panel core having interlocking expandable and contractible W-shaped and V-shaped components disposed between partition plates.
U.S. Pat. No. 4,347,887 to Brown shows a "thermal shutter". A wide band of material is folded transversely to form a double row column of adjacent cells, which may have rounded visible contours. The cells are adhesively bonded to one another. The Brown structure is symmetrical, so that both sides of the shade thus formed have essentially the same appearance.
U.S. Pat. Nos. 4,631,217, 4,676,855 and 4,677,013 to Anderson show in FIG. 3 a shade of asymmetrical construction. A rear wall section of each cell is essentially straight or linear when the shade is in its expanded position. The width of these rear wall sections thus defines the spacing of the adjacent cells, while the front of each cell, containing more material, maintains a non-linear shape.
U.S. Pat. No. 4,685,986 to Anderson shows in FIGS. 1 and 3 shades of nearly symmetrical construction and symmetrical construction, respectively. The cellular shade is formed by joining two pleated lengths of material along opposing pleats. FIG. 6 shows an asymmetrical embodiment of the invention, in which the rear wall is essentially straight when the shade is in its expanded position.
U.S. Pat. No. 4,846,243 to Schneider shows a foldable window covering formed of a wide relatively soft material folded transversely, as in the Brown patent, to yield a collapsible shade. The front surface of the shade consists of a material doubled back on itself. The successive cells are spaced in the expanded position of the shade by a relatively vertical rear wall section of each cell.
U.S. Pat. No. 4,861,404 to Neff, owned by the assignee of the present application, shows a method of making a honeycomb product from two sheets of pleated material. Alternating pleats are formed of large and small dimensions, and end parts of the large pleats then bonded together to form leg portions. These leg portions are then joined to opposing pleats of another sheet.
U.S. application Ser. No. 07/431,958, filed Nov. 6, 1989 and assigned to the same assignee as the present application, shows a Roman shade type window covering, made by joining successive folded strips of material using a manufacturing process as exemplified by U.S. Pat. No. 4,450,027 to Colson. The product in that application has substantially the same appearance as that of the present invention, but its structure and the process of manufacture are different.